Fermi LAT detection of GeV flares from the two southern-hemisphere blazars, PKS 0252-549 and PMN J2211-7039

ATel #12304; C. C. Cheung (Naval Research Laboratory), on behalf of the Fermi Large Area Telescope Collaboration
on 17 Dec 2018; 22:02 UT
Credential Certification: Teddy Cheung (Teddy.Cheung@nrl.navy.mil)

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The Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope, has observed gamma-ray flares from sources positionally consistent with the flat spectrum radio quasar PKS 0252-549 (RA = 43.3715850 deg, Decl. = -54.6976208 deg, J2000; Johnston et al. 1995 AJ 110, 880), at redshift, z=0.54 (Jauncey et al. 1978 ApJ 219, L1), and with the flat spectrum radio source PMN J2211-7039 (RA = 332.984542 deg, Decl. = -70.653722 deg, J2000; Mauch et al. 2003 MNRAS 342, 1117), with no known redshift.

Preliminary analysis indicates that the source coincident with PKS 0252-549 on 2018 Dec 15 and 16 showed a gamma-ray outburst with respective daily fluxes (E>100MeV) of (0.6 +/- 0.1) x10^-6 ph cm^-2 s^-1 and (0.5 +/- 0.1) x10^-6 ph cm^-2 s^-1 (errors are statistical only), a factor of more than 50x greater than reported in the 3FGL catalog (3FGL J0253.1-5438; Acero et al. 2015 ApJS 218, 23). The single power-law photon indices were 2.3 +/- 0.2 (Dec 15) and 2.4 +/- 0.2 (Dec 16), and comparable to the 3FGL average value of 2.45 +/- 0.12.

For the source coincident with PMN J2211-7039, preliminary analysis on 2018 Dec 16 showed a hard spectrum gamma-ray flare with daily flux (E>100MeV) of (0.3 +/- 0.1) x10^-6 ph cm^-2 s^-1, a factor ~20x greater than reported in the 3FGL catalog (3FGL J2212.3-7039; Acero et al. 2015 ApJS 218, 23). The single power-law photon index was 1.4 +/- 0.1, significantly smaller than the 3FGL average value of 2.76 +/- 0.22. High-energy photons with energy up to 65 GeV were detected.

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of these sources will continue. In consideration of the activity of these sources we encourage multiwavelength observations. The Fermi LAT contact person for these sources is C. C. Cheung (Teddy.Cheung at nrl.navy.mil).

The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.